1. Field of the Invention
The present invention generally relates to a lens. More particularly, the present invention relates to an optical lens and a lens system.
2. Description of the Related Art
In a variety of equipments such as telescope, camera, microscope or optical projection system, the optical system is an important component. Generally, in the optical system described above, the image quality is highly dependent on the lens thereof. Hereinafter, the structure of a conventional lens will be discussed in detail.
FIG. 1 is a schematic cross-sectional view illustrating a conventional lens. Referring to FIG. 1, the conventional lens 100 includes a barrel 110, a first lens 120, a baffle 130, a second lens 140, a mount 150, a filter 160 and a charge coupled device (CCD) sensor 170. The barrel 110 has a light incidence opening 110a for incidence of light and a receiving space 110b, wherein the first lens 120, the baffle 130, the second lens 140 and the mount 150 are disposed in the receiving space 110b sequentially. The baffle 130 is disposed between the first lens 120 and the second lens 140b. In addition, a portion of first lens 120 is exposed by the light incidence opening 110a. The mount 150 has a light exit opening 150a for the exit of light, wherein a portion of the second lens 140 is exposed by the light exit opening 150a. Moreover, the CCD sensor 170 is disposed on a light path after the mount 150, and the filter 160 is disposed on the light path between the mount 150 and the CCD sensor 170.
Therefore, the image quality of the conventional lens 100 is dependent on the precision of the alignment of the first lens 120 and the second lens 140. It is preferable that the optical axis of the first lens 120 and the optical axis of the second lens 140 should be coincident. However, in fact that the optical axis of the first lens 120 and the optical axis of the second lens 140 are not coincident, and thus the optical property of the conventional lens 100 is dependent on the alignment error. Referring to the enlarged view shown in FIG. 1, in the conventional lens 100, the alignment of the first lens 120 and the second lens 140 is dependent on the assembly of the first lens 120 and the second lens 140 with the inner wall of the barrel 110. Therefore, the alignment precision of the first lens 120 and the second lens 140 is influenced by the machining precision of the inner wall of the barrel 110. Recently, the machining of the barrel 110 is performed by using the computer numerical control (CNC) lathe or the CNC boring machine. However, generally the finest machining precision of the inner wall of the barrel 110 is up to about 10 μm. Therefore, the alignment error of the first lens 120 and the second lens 140 is greater than 5 μm, and thus the application of the conventional lens 100 using the barrel 110 for alignment is limited. Specially, the conventional lens 100 using the barrel 110 for alignment is not suitable for an optical instrument requiring high precision. Furthermore, the optical property of the conventional lens 100 will be analyzed by using optical simulation analysis described in the following.
FIG. 2 is a schematic drawing of the optical simulation analysis of a conventional lens. Referring to FIG. 2, a light 180 is incident onto the CCD170 via the light incidence opening 110a of the barrel 110, the first lens 120, the opening 130a of the baffle 130, the second lens 140, the light exit opening 150a of the mount 150 and the filter 160. A portion of the light 180 forms the image light source 180a and another portion of the light 180 forms an useless stray light 180b, wherein the image quality is influenced by the stray light 180b. It is noted that, a portion of the stray light 180b is formed by the reflected light of the light 180 via the filter 160, and via the interface between the first lens 120 and the second lens 140. In addition, another portion of the stray light 180b is formed by the reflected light of the light 180 via the CCD sensor 170, and via the surface of the mount 150. Although the baffle 130 disposed between the first lens 120 and the second lens 140 is composed of a black and low reflectivity material for absorbing the stray light 180b, the improvement of the baffle 130 is not obvious.